Process for the manufacture of esters of oxy-acids



' 't'rioxide, uranium oxide, copperlatented 11, 1927.

UNITED STATES PATENT OFFICE. I

mussnnni or nmnnn rxearnnrn-on 'rn-ggm, GERMANY, assmxon 'ro THE m OF C.H. IBOEHBINGEB & SOHN, .CHEKIS a imam, or emma-mann- HEIII-ON-TBE-BHINE, GERMANY, A GERMAN SOCIETY.

rnocn'ss roa 'rnn miwrac ruan or Esra-as or exit-Louis.

Io Drawing. Application fled February 20, 1925,

where R is either hydrocarbon radicle or an atom of hydrogen.

In carryin the process into' practice, the hydroxy' aci s servingasparent materials such as. for example lactic acid, glycollic acid,'andh droxy-butyric acid, ma ic acid, tartaric aci and so on, are firstconverte into the corresponding esters of these. apids.

Afterwards ..they are dehydrogenated m-a vaporized state by the actionof oxygen which advantageously n'jaytbe employed in 4 the form-of anoxygen-containing gas, for

example, air or a gaseous mixture of oxygen and ozo'ne, or may besupplied by substances yielding oxygen, for example, metallic oxideson'heatlngvoverwhici the vaporized ester mixture'passed.- During thedehydrogenation oxy-acid esters are formed by the conversion ofthealcohol group into the carbonyl group. Advantageously,'the process isperformedjwithoutdetriment to the reaction in the presence of vapours,for example steam, with the aid of which the tem-" perature and thespeed of the reaction can be, controlled so that a violent or explosivereaction is avoided with safety. If necessary, the process especially"the dehydrogenation, can be performed -'with oxygen in the presence ofcontact substances;

for such purposes used which are derived from highly 'oxi metals.Particularly effectiveare oxides of an acid character in thefree form,or combined "as salts. Good results are obtained for example byemploying the following kinds .of cata-' lysts:-Vanadium pentoxide,molybdenum and silver vanadates, molybdates, uranates, lead chromate,nickel chromate, and so on.

Furthermore, ferric oxide, nickel and coseim no. 1o,es2,

oxy-compounds may beized without being disturbed to any extent withoxygen are at a sli htly increased pressure t rough a and in (may larch5, 1m.

halt oxide... the oxides of manganese, copper oxide, the oxides of the'rare earths and others may also be employed'as catalysts.

In some cases it 1s advantageous to use 1 more than one catalyst, forexam 1e mix-v tures of several'catalysts. The cata ysts can be actlvatedby the addition of certain substances which have no catalytic action of'them own.. They may be, employed upon porous carrying substances such aspumice stone, unglazed china, asbestos and the-like, but also spreadupon metals with rough surfaces for example aluminium, iron, copper,etc. 7 K

The reaction starts apparently at ordinary tem perature orattemperatures below he process, however, is preferably carried onat.elevated temperatures for exd am le between100 and-500 C. Excellent yiedsare obtained generally by working between 200 and 400 C. ,When thelactic acid esters of'the aliphatic alcohols for example are usedasstarting material in accordance with the present process it working atabout 250-350 ticularly good results. be carried through ,at ordinary orat increased pressure, or even in a vacuum. Generally speaking, it-isbest to suit the pres- C. yielded parsure to be used to .thesensitiveness of the esters utilized in such -.a way that very sensitiveesters are treated in a vacuo, for less sensitive esters on the otherhand increased pressure is used.. I

In order to avoid the saponification of such esters as are, especiallyeasily saponified by thewater formed during the reaction it iswas foundthat The process may advisable but not essential to provide forth'presence :of agents combiningwith or fixing the water formed, as itwas noticed that even'in the absence of such means the oxidizing processcan be carried throiwh Ewamples 1. The vapours passed at atmos liericortube wit a lfngth of ten meters and an inof'lactic ester in mixtureterior Width of 2-4 centimeters,'at a moderate speed. Pyroracemie acidester is ob tained with a yield of 60 per cent of the theoretical.

2. 120 grams of the ethylester of lactic acid in the vaporous form arepassed over 400 grams of vanadium pentoxide at 250 C. About 70 gramsof-adistillate results containing 70 per cent of the pyroracemic ethylester.

3. 100 grams of lactic ethylester or methylester in the form of vapoursare mixed with an excess of oxygen, ainounting'to four to six times thequantity required by theory. The mixture is conducted over vanadiumpentoxide at a temperaturecorresponding to the boiling'point of therespective ester. 95 to 100 grams of distillate'are obtained, containing30 to 40 percent of the ester of the pyroracemic acid.

4. A mixture of the vapours of lactic methyl ester orethyl ester Withoxygen air or a mixture of carbon dioxide and oxygen in equal parts ispassed through a pipe heated to 250255 C. and charged with vanadiumpentoxide which has been precipitated Trpon' pumice stone. The vapoursobtained are cooled. The condensate "contains, according to theconditions under which the process has been carried on, 60 to 70% ofpyroracemic methyl ester or ethyl ester re spectively-in addition to afew percent of unconverted lactic acid ester and free pyroracemic acid.,The remainder consists of water formed by'the reaction.- The pyroracemicacid can be obtained in a pure state by direct fractional distillation,but can if desired, be previously salted out, and yields 60 to 7 0%ofthe theory.

5. The vapours of glycollic ethyl ester are mixed with air and themixture is passed at a pressure of one and a half to two atm0s-' pheresthrough a tube charged with silver or copper vanada-te and heated to200250 C. The working up of the product obtained and containingmore-than v50 percent of glyoxylic ethylest'er proceeds onthc linesdescribed above. .i c 6. The vapours of tartaric dicthylester are mixedwith oxygen and the mixture is passed at 300 C. and at a pressure of 60millimeters over pieces of unglazed china which are coated with theoxides of vanadium or uranium, or over pieces'iof sheet aluminiumtreated in the same way. The. condensate contains 50-60 percent diketosuccinic diethylester besides a small quantity of ketomalonicdiet-hylester. In the same or a similar manner other oxy acid esters maybe prepared, for example glyoxylic butylester" from glycollic-'butylester, pyroracemic amylester from lactic amylester, a-keto butyricester frgm a-hydroxybutyric ester, oxalacetic diethylester from malicdiethyl ester, etc. The oxyacid dehydrogenating the vapours so producedby the action of oxygen.

2. Process for the manufacture of esters of oxyacids which consists inconverting the hydroxy acids into the corresponding volatilizableesters, andsubsequently dehydro genating the latter in a vapourized formby the action of oxygen." p 3. Process for the manufacture of esters ofoxyacids which consists in volatilizing the esters of hydroxy acids andsubsequently dehydrogenating the same by means of oxygen-containinggaseous mixtures.

. 4. Process for the manufacture of esters of oxyacids which consistsinconverting the hydroxy acids into the corresponding va-.

porizable esters and subsequently dehydrogenating the latter in avaporized state by,

the action oxygen-containing gaseous mixtures. 1 4

5. Process for the manufacture of esters of oxyacids Which consists involatilizing the esters of the hydroxy acids and subsequentlydehydrog'enating the same by the action of gaseous mixture contalmngoxygen and ozone.

6. Process for the manufacture of esters of oxyacids which consists inconverting the hydroxy acids into the corresponding volatiliz'ableesters and subsequently dehydrogenating-the latter in a vaporized stateby the action of gaseous mixturecontaining oxygen and ozone.

7 ."Process for. the manufacture of esters of oxyacids which consists involatilizing the esters of hydroxy acids and subsequentlydehydrogenating the latter by the action of air containing ozone.

. 8. Process for the manufacture of esters of oxy acids which consistsin volatilizing *the esters of hydroxy acids and subsequentlydehydrogenating the same by the action of oxygen in the presence ofinjected steam.

9. Processforthe manufacture of esters of oxy acids which; consistsinvaporizing the esters of hydroxy acids and subsequently dehydrogenatingthe latter by means of gaseous mixture containing oxygen in the presenceof injected steam.

10. Process for the manufacture of esters of oxy acids which consists invaporiz ng the esters of hydroxy acids and subsequently dehydrogenatingthe same by the action of acting oxygen compounds which are derived fromhighly oxidized metals.

11. Process for the manufacture of esters of oxy the h droxy acids intothe corresponding volati izable esters and subsequently dehydrogenatingby the action of oxygen in thev presence of oxygenicom ounds which arederived from highly oxidized metals.

12. Process for the manufacture of esters of oxy acids which consists'involatilizing the esters of hydroxy acids and subsequentlydehydrogenating the latter by the action of oxygen in the presence ofoxides of an acid character which are derived from highly oxidizedmetals.

13. Process for the manufacture of esters of oxy acids which consistsinvolatilizing the' esters of hydroxy acids and subsequently.dehydrogenating the latter bythe action of oxygen at temperatures ofabout 100 C; to about 500 C. f f

14. Process for the manufacture of esters acids which consists in.converting" the latter in a vaporized statev of oxy acids which consistsin volatilizing the esters of hydroxy acids and subsequentlydehydrogenating the latter bythe action of oxygen at temperatures ofabout 200 about 400 C.

15/ Process for the manufacture of the esters of pyroracemic acid whichconsists in 'volatilizing lactic acid ester and subsequent- 1y dehdrogenating the vapours by the action 0 oxygen:

16; Process for the manufacture of esters of keto-com ounds whichconsists in volatilizing' the actic acid esters of alphatie alcohols andsubsequently dehydrogenating the vapours by the action of oxygen.

17. Process for the production of aliphatic esters of pyroracemic acid,which consists in' volatilizmg the lactic acid esters of aliphaticalcohols and subsequently dehydrogenating the same by the action oioxygen at temperatures varying between arm-350 C. a

In testimony whereof I aflix my signature. l

ALFRED HAUSSLER.

